1 /* Copyright 2013 Google Inc. All Rights Reserved. 2 3 Distributed under MIT license. 4 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT 5 */ 6 7 /* Utilities for building Huffman decoding tables. */ 8 9 #ifndef BROTLI_DEC_HUFFMAN_H_ 10 #define BROTLI_DEC_HUFFMAN_H_ 11 12 #include <brotli/types.h> 13 #include "./port.h" 14 15 #if defined(__cplusplus) || defined(c_plusplus) 16 extern "C" { 17 #endif 18 19 #define BROTLI_HUFFMAN_MAX_CODE_LENGTH 15 20 21 /* Maximum possible Huffman table size for an alphabet size of (index * 32), 22 * max code length 15 and root table bits 8. */ 23 static const uint16_t kMaxHuffmanTableSize[] = { 24 256, 402, 436, 468, 500, 534, 566, 598, 630, 662, 694, 726, 758, 790, 822, 25 854, 886, 920, 952, 984, 1016, 1048, 1080}; 26 /* BROTLI_NUM_BLOCK_LEN_SYMBOLS == 26 */ 27 #define BROTLI_HUFFMAN_MAX_SIZE_26 396 28 /* BROTLI_MAX_BLOCK_TYPE_SYMBOLS == 258 */ 29 #define BROTLI_HUFFMAN_MAX_SIZE_258 632 30 /* BROTLI_MAX_CONTEXT_MAP_SYMBOLS == 272 */ 31 #define BROTLI_HUFFMAN_MAX_SIZE_272 646 32 33 #define BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH 5 34 35 typedef struct { 36 uint8_t bits; /* number of bits used for this symbol */ 37 uint16_t value; /* symbol value or table offset */ 38 } HuffmanCode; 39 40 /* Builds Huffman lookup table assuming code lengths are in symbol order. */ 41 BROTLI_INTERNAL void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* root_table, 42 const uint8_t* const code_lengths, uint16_t* count); 43 44 /* Builds Huffman lookup table assuming code lengths are in symbol order. */ 45 /* Returns size of resulting table. */ 46 BROTLI_INTERNAL uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table, 47 int root_bits, const uint16_t* const symbol_lists, uint16_t* count_arg); 48 49 /* Builds a simple Huffman table. The num_symbols parameter is to be */ 50 /* interpreted as follows: 0 means 1 symbol, 1 means 2 symbols, 2 means 3 */ 51 /* symbols, 3 means 4 symbols with lengths 2,2,2,2, 4 means 4 symbols with */ 52 /* lengths 1,2,3,3. */ 53 BROTLI_INTERNAL uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table, 54 int root_bits, uint16_t* symbols, uint32_t num_symbols); 55 56 /* Contains a collection of Huffman trees with the same alphabet size. */ 57 typedef struct { 58 HuffmanCode** htrees; 59 HuffmanCode* codes; 60 uint16_t alphabet_size; 61 uint16_t num_htrees; 62 } HuffmanTreeGroup; 63 64 #if defined(__cplusplus) || defined(c_plusplus) 65 } /* extern "C" */ 66 #endif 67 68 #endif /* BROTLI_DEC_HUFFMAN_H_ */ 69
